Cellulose-ether film and composition for making the same



Patented June 11, 1929.,

i 5 k a t r a it 1..

STEWART J. CARROLL, OF ROCHESTER, NEW YORK, ASSIGNOR T0 EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK. l

CELLULOSE-ETHER FILM AND COMPOSITION FOR ING THE SAME.

No Drawing.

This invention relates to compositions of matter in which cellulose ethers, such as water-insoluble ethyl cellulose, are combined or mixed with other substances which impart not only low infiammability, but likewise give compositions the other properties of which are also highly advantageous in the plastic and analogous arts, such, for instance, as the film or varnish arts.

One object of the invention is to provide cellulose ether films having not only all of the ordinary desirable qualities of films for photographic purposes, but also having unusually low inflammability and extremely high resistance to deterioration by heat.

Another object of the invention is to provide permanently transparent, strong, flexible sheets or films of desired thinness, which are substantially waterproof, are unaffected by ordinary photographic fluids, are substantially colorless, are substantially without harmful action upon light-sensitive photographic coatings, are of low inflammability and highly resistant to prolonged heating. Another object of the invention is to provide compositions capable of easy manipulation in film making, varnish making, or allied plastic arts. Another object is to provide compositions which will not injure .or be injured by the substances or surfaces with which they are associated during manufacture, storage or use. Other objects will hereinafter appear.

In U. S. Patent No. 1,188,376, Lilienfeld, June 20th. 1916, there are disclosed a series of alkyl ethers of cellulose. Certain of these are particularly insoluble in water, and the present invention finds its chief value in connection with ethers having this property, such as water-insoluble ethyl cellulose, films of which have small shrinkage characteristics, after treatment in photographic baths. In U. S. Patent No. 1,583,709, Webb, May 4th. 1926, there are disclosed films of such cellulose others in which the ordinary desirable qualitiesof photographic film base are combined with resistance to prolonged heating, this result being brought about by maintaining an alkalinity in excess of Ph,. It is desirable that such films, especially motion-picture films, be capable of withstanding heating without becoming brittle. Whether or not films will possess this prop- Application filed August 9, 1926. Serial No. 128,335.

erty can be foretold with practical accuracy by testing samples, say by heating them for weeks and even months at a continuous temperature of 65 C. Films which remain usefully flexible after such a severe test are capable of withstanding the conditions met with in use.-

I have found that these qualities of the films may be maintained and yet the inflammability greatly lowered by incorporating in such films and in the compositions out of which they are made, one or more of the brom-nucleo substitution products of phenols and their homologues, such, for example, as mono, di, or tri or other poly brom,phcnol, catechol, resorcinol, hydrochinone, pyrogallol, phloroglucinol, cresol and thymol. Where ortho, meta or para isomers exist, they are all usable. On account of their relative cheapness and simplicity of manufacture, I prefer tribromphenol, parabromphenol and brom hydrochinone. All of these substances, when mixed into the filmmaking compositions, should be free from free bromine and free hydrobromie acid. Otherwise they will cause sufficient discoloration to make the film undesirable for photographic purposes, Will cause deterioration of any photographic emulsions placed upon the film, and will destroy the alkalinity upon which the resistance of the film to prolonged heating depends.

In the Technology of Cellulose Esters by E. C. Worden, Volume VIII, published in 1916 by D. Van Nostrand Company of New York, N. Y., page 2668, it is stated that tribromphe-nol in cellulose acetate plastics gives colored compounds which become acid upon standing. It, therefore, might have been expected that tribromphenol would be particularly unsuitable for cellulose other films, because the development of acidity in them would induce brittleness upon prolonged heating. Not only would the discoloration make it undesirable, but the tendency to brittleness would be fatal.

But I have found, as stated above, that if the brominated phenols are initially purified from free bromine and free hydrobromic acid and are incorporated in films having an alkalinity greater than Ph,, there is no acidity in the film-making solution, nor in the film, nor does this condition develop during the normal storage of the solution or during the normal use 111 life of the film in the appended claims. 100 parts by weight of water-insoluble ethyl cellulose containing .suiiicient alkali, say by undergoing the treatment given in lines 78 to 92 of page 1 in the above cited Webb patent, are dissolved along with 5 to 50 (say 20 parts) of tribromphenol in 300 to 500 parts of'a' volatile common solvent. The latter may usefully comprise a mixture of methyl acetate and methyl alcohol, the weight of the methyl acetate. being approximately nine times the weight of the methyl alcohol. Of course, the ingredients of the solvent are of suliicient purity to avoid acidifying the composition. This composition is suitable for spreading upon a filmforming surface in a coating, from which the volatile solvent evaporates sufliciently to leave a transparent, flexiblesheet, which is stripped off and otherwise treated in a manner well known to those skilled in this art.

. In place of the tribromphenol, an equal numher of parts by weight can.be substituted of any one of the brominated phenolic bodies mentioned hereinabove, or mixtures of them. By reason of the fact that these brominated products are of the nucleo type, having the bromine atoms directly bonded to the ring of carbon atoms, they are particularly stable.

The ingredients in the film-forming composition are thoroughly mixed and may be filtered if desired. When more fiowable solutions are desired, or when the compositions are to be employed as lacquers. the volatile solvent may be increased until the desired viscosity is obtained, or volatile liquids, such as benzol. alcohol, and the like may be added to the thinner. Along with the ingredients mentioned above, I may add one or more supplementary organiobodies of only slight volatility which enhance the flexibility of the compositions and regulate the preparation of film therefrom; but such bodies are not essential. Examples of them are amyl or butyl acetate, the various amyl alcohols, the various butyl alcohols, and mixtures of them. Of course, these ingredients are also sufiiciently pure to be non-acid.

Films prepared from the hereinabove described compositions are flexible, smooth, transparent, strong, substantially colorless, substantially waterproof, are unaffected by ordinary photographic baths, and in addition, combine unexpectedly low inflammavbility with high resistance against brittleness upon prolonged heating at (3., or equiva ent conditions in actual use. The

amount of alkali in the films is, of course, in-

sufiicient to impair their transparency.

I shall now give one example of my in Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

water-insoluble cellulose ether, a brom-nucleo .bromic acid, and a solvent common to said ingredients, said composition being stabilized by the presence therein of inorganic alkali which creates an alkalinity in the composition in excess of Ph,, the proportions being such that a product formed therefrom will have the properties of high transparencies, freedom from accidental color, incrtness toward photographic emulsions and high resistance to heating.

2. The composition of matter comprising substantially the following: 100 parts by weight of water-insoluble ethyl cellulose; 20 parts of tribromphenol, and more than 300 parts of a volatile common solvent, said composition comprising sufiicient inorganic alkali to give it an alkalinity in excess of Ph,.

3.-A fiowable composition comprising 100 parts by weight of water-insoluble ethyl cellulose, 5 to 50 parts of tribromphenol substantially free from uncombined bromine and hydrobromic acid, and more than 300'parts of a volatile common solvent, said composition comprising sufficient inorganic alkali 1. A fiowable composition comprising a i substitution product of the phenols and their to give it an alkalinity in excess of Ph,, the

dental color, incrtness toward photographic.

emulsions and high resistance to heating.

4. As an article of manufacture a film comprising colloidized water-insoluble cellulose ether and a brom-nucleo substitution product of the phenols and their homologues, said product being substantially free from uncombined bromine and hydroln'olnic acid, said film having distributedtherein suflicient inorganic alkali to give the film an alkalinity in excess of P11 the proportions ofthe ingredients being such that the film is flexible, transparent and inert to photographic emulsions.

5. As an article of manufacture a film comprising colloidized water-insoluble ethyl cellulose and tribromphenol free from uncombined bromine and hydrobromic acid, said film having uniformly distributed there in sufficient inorganic alkali to give the film an alkalinity in excess of Ph,, the amount of alkali being insuflicient to impair the transparency of the film, the proportions of the ingredients being such that the film is fiexible, transparent and inert to photographic emulsions.

Signed at Rochester, New York, this 29th day of July, 1926.

STEWART J. CARROLL. 

